The invention relates to pipe fittings for use in conveying drainage fluid, and in particular for use in conveying condensate that is drained from a drain pan of an air-cooling (de-humidifying) unit.
As a fundamental part of the physics of cooling, all air conditioners extract water from the air when they are in the cooling mode. This water, known as condensate, must be removed from the air conditioning unit and piped to outside the building. If this is not adequately or correctly done, the condensate water will overflow the drain pan of the air conditioner (as used herein “air conditioner” refers to standard air conditioners, heat pumps and to any type of de-humidifying unit), possibly causing extensive water damage to the building structure and/or building finishes and/or the contents of the building. The overflow of condensate also can provide ideal conditions for the growth of mold in those areas that are continually wetted and can seriously compromise the air quality inside the building, as well as possibly have adverse affects on the health of the occupants. Some systems for preventing condensate overflow are described on U.S. Pat. No. 6,976,367, the disclosure of which is incorporated herein by reference in its entirety. Also see U.S. Pat. No. 5,069,042 and U.S. Pat. No. 5,522,229, the disclosures of which are incorporated herein by reference in their entireties.
The condensate drain outlet of a central air conditioning unit is a critical part of the operation of the air conditioner because it forms the primary exit point for the condensate water that is collected in the drain pan inside the air conditioning unit when it is operating in the cooling mode. Currently, most drain pans have two outlets. The first (lower) outlet provides primary drainage of the condensate water, and the other outlet is a secondary (upper) outlet to provide a backup overflow outlet in case of a blockage in the primary drain outlet. Typically, the secondary outlet is situated ½-¾ inches above the primary outlet to ensure that any condensate water produced will first run out of the lower primary outlet. The secondary outlet will only become operative if there is an increase in the water level due to a blockage in the lower or primary drain outlet, causing the water to then run out from the secondary outlet. An example of a drain pan having primary and secondary drain outlets can be found in U.S. Pat. No. 5,755,105, the disclosure of which is incorporated herein by reference in its entirety.
Current designs of central air conditioning systems utilize this dual outlet system to evacuate the condensate water produced when the unit is in a cooling mode. All manufacturers of air conditioning units routinely and specifically require that their equipment is fitted with a trap as part of the installation process. A number of local building codes and some national building codes also mandate the use of traps just downstream of the primary drain outlet. The purpose of the trap is to ensure that any condensate water that is produced can flow freely out through the drain pipe system through the force of gravity, while at the same time ensuring that no air can pass through the trap in either direction. The water seal formed by the trap thus prevents cool air from inadvertently exiting through the drainage line, while preventing warm air from entering the cooling system through the drainage line.
It is absolutely imperative that the trap and the connecting stub that is fitted to the primary drain outlet of the air conditioning unit are correctly oriented. That is, the trap and connecting stub must be oriented with sufficient slope to ensure unimpeded flow of condensate liquid out of the drain pan of the air conditioning unit. If this is not done, the condensate water will not be able to flow freely, and may back-up inside the drain pan. If an overflow switch has been provided in the drain pan, such back-up will cause the overflow switch to operate every time the unit runs in the cooling mode, causing many unnecessary return visits by a technician. If no overflow switch has been fitted, the condensate water may overflow the drain pan, causing damage inside the unit and possibly leading to damage to the building and potential mold growth.
Some air conditioning units are designed with a built-in slope in the drain pan to promote proper drainage. However, if the air conditioning unit is installed with a slope in the opposite direction, it can negate this drain pan slope and cause the condensate flow to back-up. Even if the drain pan is properly oriented, an improperly oriented drainage flow system downstream of the drain pan (for example, a drainage flow system with an upward slope) could cause the drain pan to overflow by preventing the gravity flow of liquid out of the drain pan.